1. Field of the Invention
This invention relates to packaging. In particular, the invention relates to stacking integrated circuit (IC) devices.
2. Description of Related Art
Demands for high density boards in microprocessor systems have created many challenges to the board assembly process. Among several methods, stacking multiple integrated circuit (IC) devices saves a significant amount of space on printed circuit board (PCB).
The next generation memory modules run at very high frequencies such as the Double Data Rate 2 (DDR2) dynamic random access memory (DRAM). The operating frequencies may range from 133 MHz to 1 GHz or higher. The packaging of these devices needs to be changed to more advanced packaging techniques such as Ball Grid Array (BGA) to maintain performance characteristics. Existing techniques to stack multiple devices in other chip packages are not applicable to the BGA packaging. Furthermore, even for other chip packages, existing techniques have a number of disadvantages such as mechanical weakness, low signal integrity, high manufacturing costs, etc.
Therefore, there is a need to have an efficient technique to stack multiple IC devices.